Precession cameras were widely used in protein X-ray crystallography in earlier days. Their advantage is that they give an undistorted image of the reciprocal space of lattice planes (Fig. 1). Moreover, the symmetry in the crystal and its space group can easily be determined and the crystal quality checked. The precession camera is not suitable for efficient three-dimensional data collection because it records only one lattice plane in each exposure. Therefore, it is no longer a popular instrument in protein X-ray crystallography.
